Fabrication And Pseudocapacitive Properties Of Bimetallic Sulfides Based On Nickel Cobalt Manganese

This work focus on synthetising and studing the electrochemical performance of bimetallic sulfides based on nickel,cobalt,and manganese.There are some original researches on tuning component,morphology design,and fabrication of aqueous asymmetric supercapacitors.The detailed results are following:1.Sea urchin-like nanotube structure has much higher specific area,and its hollow tube is beneficial for ions diffusion and electron transfer.In this part,nickel cobalt?Ni–Co?sulfides with different stoichiometric Ni to Co ratios have been successfully synthesized based on a facile anion-exchange reaction.The result shows that all of the Ni–Co sulfides share similar sea urchin-like structures with numerous nanotubes extend outward from the center.The electrochemical performance of Ni–Co sulfides can be tuned owing to the synergistic effect between Ni and Co ions.The bimetallic Ni–Co sulfides show much higher specific capacity than monometallic Co sulfide.Especially,the Ni_0.25Co_0.75 sulfide shows superior electrochemicalperformance,which delivers the highest specific capacityof 1300F?g^-11 at 1 A?g^-1 combined with excellent cycling stability.2.A series of Co_xMn_3-x sulfides?x=0³?were prepared by a facile one step solvent-thermal route.The crystal structure,morphology and electrochemical performance of Co-Mn sulfide can be tuned successfully by varying different Co/Mn ratios.As the Co/Mn ratio increases,the phase structure tends to be low crystallization,the morphology varies from rock-like steuture to flower-like laminar nanostructure,and the electrochemical performance is improved,which can be ascribed to the synergistic effect between Co ions and Mn ions.Co_2.5Mn_0.5 sulfide exhibits the highest specific capacitance,best rate capability and excellent cycling stability.Moreover,an asymmetric device using Co_2.5Mn_0.5 sulfide//RGO shows high energy density of 22.3 Wh?kg^-1 at a power density of 750 W?kg^-1,as well as excellent cycling performance with 85%retention after 5000cycles.3.A facile two-step hydrothermal route was adoped to synthesized urchin-like Co-Mn sulfide and further used Ni foam as substrate to design hierarchical architecture Co-Mn sulfide nanowire arrays on Ni foam.After electrochemical tests,the Co-Mn sulfide supported on Ni foam exhibits improved performance of 984F?g^-1 at 1 A?g^-1 as well as remarkable cycling stability with 107%of initial value retention after 2000 cycles.In addition,a hybrid supercapacitor Co-Mn sulfide@Ni foam//RGO nanosheets is assembled and displayed ultrahigh power density and outstanding cycling stability?98%coulombic efficiency after 3000 cycles?.The excellent electrochemical performance can ascribe to its unique structure with porous and rough surface of nanowires on 3D Ni foam which can effectively shorten the diffusion of ions and accelerate the transfer of electrons.